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Viscous Coupling

NOTE: The viscous coupling and pinion assembly is not a serviceable component. It is a sealed unit and is not refillable. If the coupling or pinions become damaged in some way, the unit must be replaced as an assembly. Do not attempt to disassemble the unit. In the two-wheel drive mode, the transfer case shift fork and clutch sleeve are not engaged with the spline gear and sprocket carrier. This disconnects the drive sprocket from the main shaft and prevents torque transfer through the drive train to the driven sprocket, front output shaft and front propeller shaft.

Torque Bias Check

A method for checking the viscous coupling operation, both in and out of the automobile, has been developed. The procedure involves measuring the torque required to rotate the coupling when it is in a static (at rest) condition. Whenever diagnosis indicates a possible coupling malfunction, check the coupling torque bias (static rotating torque) as outlined in the following two procedures.

In-Automobile Torque Bias Check
Place the automobile on a level surface. Stop the engine.

Place the transmission shift lever in Neutral. Place the Select Drive lever in the four-wheel
drive mode. (before shutting off engine)

Raise one front wheel off the floor.

Remove the hub cap from the raised wheel.

Assemble a socket and torque wrench and install on any lug nut of the raised wheel.

Rotate the wheel using the torque wrench and measure the torque required to rotate the wheel.

If the coupling is operating properly, it should require a minimum of 61 N·m (45 ft-lbs) torque to rotate the wheel.

If the rotating torque is at or above the specified limit, remove the wrench, install the hub cap and lower the wheel.

If the rotating torque is below the specified limit, remove the wrench, install the hub cap, lower the wheel and refer to On-Bench Torque Bias Check.

Transfer Case Shift Motor troubleshooting

v990923